U.S. Pat. Nos. 4,877,313 and 5,002,701 describe light valves, particles useful in a light valve suspension and light valve suspensions, and are incorporated herein by reference thereto. In these patents, a light polarizing material containing adsorbed iodine, is described as being comprised of a complex obtained by reacting (i) elemental molecular iodine, (ii) a hydrohalide acid and/or an ammonium or alkali metal or alkaline earth metal halide, and (iii) a precursor compound. The reaction may take place in the presence of a protective colloid, such as nitrocellulose. These particles are suspended in a liquid suspending medium to form a light valve suspension.
It is particularly useful that the particle size of the particles suspended in the light valve suspension are not too large (generally on the order of about 1 micron or less) in order to maintain the particles in a suspension without agglomeration or precipitation during repeated on-off cycles of the light valve. Obtaining particles of appropriate colloidal size, however, has been generally unpredictable and has been believed to be a function of the specific combination and character of the reaction materials used to form the particles and various crystallization conditions and parameters. Breaking up of large particles may affect the ability of the particles to function as light valve particles. It would therefore be desirable to initially form the particles in the appropriate size dimensions.
It is accordingly an object of the present invention to provide crystals of a light polarizing material of a size suitable for use in a light valve suspension.
It is a further object of the present invention to provide means for forming the suitable size of particles of light polarizing crystals as the particles of the light polarizing material are initially formed.
These and other objects, features and advantages of the present invention will become more evident from the following discussion.